1. Field of the Invention
The present invention relates to aircraft with electric flight controls including a fuselage able to deform and vibrate longitudinally and laterally with the formation of vibration nodes and antinodes distributed along the longitudinal axis of the aircraft. It relates quite particularly to long-length airplanes which have high longitudinal flexibility. However, it advantageously applies equally well to airplanes of a shorter length and lower flexibility.
2. Discussion of the Background
It is known that an aircraft with electric flight controls has flight controls such as sticks, mini sticks, rudder bars, etc., which are equipped with electric transducers so that they generate electric flight control datums representative of the action that a pilot exerts on them. It also includes a flight control computer which, on the basis of the electric flight control datums generated by the flight controls and of flight control parameters originating, for example, from sensors, formulates electric commands that the flight control computer applies to actuators tasked with moving the control surfaces of the aircraft.
It is also known that aircraft with electric flight controls are provided with an inertial reference system (generally known as an IRS) including elements useful in navigation, such as the inertial unit, and elements useful in flight control, such as gyrometers and accelerometers. Finally, it is known that all these elements, whether they have to do with navigation or flight control, are grouped together in an IRS unit arranged at a given point on the aircraft. Of course, as a result, this IRS unit is subjected to the action of the deformations of the fuselage, which deformations occur mainly along the axes of pitch and yaw under the effect of the turning of the control surfaces or the effect of external disturbances.
Because of the high time constant attached to the elements useful in navigation, such deformations have only a small action thereon. By contrast, in order to get around the problems of interaction between the deformations of the fuselage and the elements useful in flight control, it is essential to have filtering means on the control surface control lines.
However, in the case of aircrafts with high longitudinal flexibility, the deformations become greater, which means that it is then necessary to perform extremely intense filtering of the control lines, and this introduces significant phase shifts thereinto and therefore detracts greatly from the performance of the control lines.